(1) Field of the Invention
This invention relates to a vertical shaft V-type engine work vehicle such as a power lawn mower.
(2) Description of the Prior Art
Some power garden machinery particularly for lawn mowing are equipped with vertical shaft V-type engines, with their crankshaft mounted in vertical position on the mower deck.
In relatively small-sized and hand-push type models, these engines are mostly of single cylinder arrangement. With some so-called riding type mowers and those hand-push models for commercial application, however, the horizontal opposed-type two-cylinder engine is employed in which the cylinders are arranged vertically, one above the other. One example of such an engine is shown in FIGS. 5 and 6, which is of side valve type.
The horizontal opposed-type engine shown has a pair of cylinders 18, each having a piston 19 mounted therein. The paired cylinders 18 are placed to axially oppose each other and each have a connecting rod 20. A crankshaft 11 is housed in a crankcase 17 and has a pair of crank pins 21 to which the connecting rods 20 are connected respectively.
However, these horizontal opposed-type engines have some dimensional disadvantages. First, as best shown in FIG. 5, because of the head-to-head arrangement of the paired cylinders 18, the constructed body of the engine comes to have an increased width W1. Thus, the bonnet in which the engine is installed necessarily becomes enlarged in lateral dimension in front of the operator. Secondly, as seen in FIG. 6, there is a limitation in reducing the engine height H1, without mention of the additional increase in height compared with the single-cylinder design. This limitation results from the fact that the technical need for operating the paired crank pins, which are jointed to their respective connecting rods on both side of the crankshaft (FIG. 5), in a displaced phase from each other, along with the minimum required rod length, does not allow the piston pin pitch P1, the distance between the two piston pins, to occur below a minimum distance. Consequently, the bonnet could not be smaller than a minimum height.
These increased height and width in the bonnet construction have resulted an increase in the range of dead ground just in front of the bonnet, to the great inconvenience of the operator particularly when he has to manipulate the machine near a tree or around the corner of a garden driving from the driver seat to make precise small turns or cornering.